From the standard model to grand unification

1982 ◽  
Vol 304 (1482) ◽  
pp. 69-86 ◽  
Keyword(s):  
Structure Constant ◽  
Fine Structure Constant ◽  
Grand Unification ◽  
Quark Masses ◽  
Grand Unified Theories ◽  
The Standard Model ◽  
Unified Theories ◽  
Order Of Magnitude ◽  
Near Future ◽  
The Universe

This paper reviews the limitations o f the standard SU (3) x SU (2) x U (l) model and develops the philosophy of grand unification. Some simple grand unified theories are presented, and calculations made of the order of magnitude of the fine-structure constant a, as well as of sin 2 0 W and some quark masses. Predictions for nucleon decay and neutrino masses are then discussed; they may be observable in the near future. It is suggested that grand unified theories complex enough for the understanding of the baryon asymmetry of the Universe may also predict a neutron electric dipole moment large enough to be measured. Finally, some inadequacies of GUTs are mentioned.

scholarly journals Unification and supersymmetry

1983 ◽  
Vol 310 (1512) ◽  
pp. 279-292 ◽  
Keyword(s):  
Fine Structure ◽  
Weak Interactions ◽  
Structure Constant ◽  
Fine Structure Constant ◽  
Fundamental Constants ◽  
Quark Masses ◽  
Fundamental Particles ◽  
Grand Unified Theories ◽  
Mixing Parameter ◽  
Unified Theories

Current attempts to construct unified theories of fundamental particles and their interactions are described, with emphasis on their ability to understand the values of the fundamental constants. Examples include grand unified theories, which enable one to estimate the fine structure constant, the neutral weak interaction mixing parameter and certain quark masses. Finally, a review will be presented of the prospects offered by supersymmetry for understanding the scale of the weak interactions and for an eventual unification with gravity.

scholarly journals Beyond the Standard Model at LEP

1991 ◽  
Vol 336 (1642) ◽  
pp. 247-259 ◽  
Keyword(s):  
Dark Matter ◽  
Standard Model ◽  
Beyond The Standard Model ◽  
Grand Unified Theories ◽  
The Standard Model ◽  
Unified Theories ◽  
Massive Neutrinos ◽  
Supersymmetric Particles ◽  
The Universe

LEP data constrain severely many proposed extensions of the Standard Model. These include: massive neutrinos, which are now largely excluded as candidates for the dark matter of the Universe; supersymmetric particles, the lightest of which would still constitute detectable dark matter; technicolour, of which many favoured versions are now excluded by precision electroweak measurements; and grand unified theories, of which LEP data favour supersymmetric versions.

Physics beyond quarks and leptons

1986 ◽  
Vol 404 (1827) ◽  
pp. 273-284
Keyword(s):  
Standard Model ◽  
Experimental Tests ◽  
Building Blocks ◽  
Beyond The Standard Model ◽  
Grand Unified Theories ◽  
The Standard Model ◽  
Unified Theories ◽  
Complete Theories ◽  
Near Future

Quarks and leptons are used as basic building blocks in the construction of more complete theories beyond the standard model. Some of these are discussed, including grand unified theories and supersymmetry. The prospects for experimental tests of these ideas both now and in the near future are reviewed.

Frontiers of Physics

2017 ◽  
Author(s):  
Nicholas Manton ◽  
Nicholas Mee
Keyword(s):  
Standard Model ◽  
Beyond The Standard Model ◽  
Epr Paradox ◽  
Grand Unified Theories ◽  
Alternative Description ◽  
The Standard Model ◽  
Unified Theories ◽  
Modern Physics ◽  
The Universe

Despite the overwhelming successes of modern physics, there are questions that remain to be answered and these are considered in the final chapter. The interpretation of quantum mechanics is discussed, including the EPR paradox, the Aspect experiments and quantum entanglement. Next, the question of whether particles are really point-like and the possibility of an alternative description in terms of solitons is considered. The Skyrmion and the Standard Model sphaleron are described. Unexplained features of the universe, such as the matter–antimatter asymmetry, the existence of dark matter and the even more mysterious dark energy, are discussed. There is also a critique of the loose ends of the Standard Model and the need for a quantum theory of gravity. The chapter concludes with a look beyond the Standard Model at the arguments and evidence in favour of Grand Unified Theories and ultimately string theory.

Water, Water, Here and There

2018 ◽  
Author(s):  
Steven E. Vigdor
Keyword(s):  
Quark Mass ◽  
Mass Difference ◽  
Baryon Number ◽  
Electroweak Phase Transition ◽  
Hydrogen Burning ◽  
Quark Masses ◽  
Grand Unified Theories ◽  
Down Quark ◽  
Unified Theories ◽  
The Stability

Chapter 4 deals with the stability of the proton, hence of hydrogen, and how to reconcile that stability with the baryon number nonconservation (or baryon conservation) needed to establish a matter–antimatter imbalance in the infant universe. Sakharov’s three conditions for establishing a matter–antimatter imbalance are presented. Grand unified theories and experimental searches for proton decay are described. The concept of spontaneous symmetry breaking is introduced in describing the electroweak phase transition in the infant universe. That transition is treated as the potential site for introducing the imbalance between quarks and antiquarks, via either baryogenesis or leptogenesis models. The up–down quark mass difference is presented as essential for providing the stability of hydrogen and of the deuteron, which serves as a crucial stepping stone in stellar hydrogen-burning reactions that generate the energy and elements needed for life. Constraints on quark masses from lattice QCD calculations and violations of chiral symmetry are discussed.

scholarly journals New Limit on Space-Time Variations in the Proton-to-Electron Mass Ratio from Analysis of Quasar J110325-264515 Spectra

Symmetry ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 344
Author(s):  
T. D. Le
Keyword(s):  
Fine Structure ◽  
Structure Constant ◽  
Space Time ◽  
Fine Structure Constant ◽  
Electron Mass ◽  
Mass Ratio ◽  
Quasar Spectra ◽  
Time Variations ◽  
Using Data ◽  
The Universe

Astrophysical tests of current values for dimensionless constants known on Earth, such as the fine-structure constant, α , and proton-to-electron mass ratio, μ = m p / m e , are communicated using data from high-resolution quasar spectra in different regions or epochs of the universe. The symmetry wavelengths of [Fe II] lines from redshifted quasar spectra of J110325-264515 and their corresponding values in the laboratory were combined to find a new limit on space-time variations in the proton-to-electron mass ratio, ∆ μ / μ = ( 0.096 ± 0.182 ) × 10 − 7 . The results show how the indicated astrophysical observations can further improve the accuracy and space-time variations of physics constants.

scholarly journals Challenges for a QCD axion at the 10 MeV scale

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Jia Liu ◽  
Navin McGinnis ◽  
Carlos E. M. Wagner ◽  
Xiao-Ping Wang
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Structure Constant ◽  
Fine Structure Constant ◽  
Multiple Sources ◽  
Standard Model Extension ◽  
Mixing Angles ◽  
Quark Masses ◽  
Model Extension ◽  
The One

Abstract We report on an interesting realization of the QCD axion, with mass in the range $$ \mathcal{O} $$ O (10) MeV. It has previously been shown that although this scenario is stringently constrained from multiple sources, the model remains viable for a range of parameters that leads to an explanation of the Atomki experiment anomaly. In this article we study in more detail the additional constraints proceeding from recent low energy experiments and study the compatibility of the allowed parameter space with the one leading to consistency of the most recent measurements of the electron anomalous magnetic moment and the fine structure constant. We further provide an ultraviolet completion of this axion variant and show the conditions under which it may lead to the observed quark masses and CKM mixing angles, and remain consistent with experimental constraints on the extended scalar sector appearing in this Standard Model extension. In particular, the decay of the Standard Model-like Higgs boson into two light axions may be relevant and leads to a novel Higgs boson signature that may be searched for at the LHC in the near future.

scholarly journals Searching for space-time variation of the fine structure constant using QSO spectra: overview and future prospects

2009 ◽  
Vol 5 (H15) ◽  
pp. 304-304
Author(s):  
J. C. Berengut ◽  
V. A. Dzuba ◽  
V. V. Flambaum ◽  
J. A. King ◽  
M. G. Kozlov ◽  
...  
Keyword(s):  
Nuclear Reactor ◽  
Structure Constant ◽  
Big Bang ◽  
The Other ◽  
Fine Structure Constant ◽  
Spatial And Temporal Variation ◽  
Fundamental Constants ◽  
Future Prospects ◽  
Big Bang Nucleosynthesis ◽  
The Universe

Current theories that seek to unify gravity with the other fundamental interactions suggest that spatial and temporal variation of fundamental constants is a possibility, or even a necessity, in an expanding Universe. Several studies have tried to probe the values of constants at earlier stages in the evolution of the Universe, using tools such as big-bang nucleosynthesis, the Oklo natural nuclear reactor, quasar absorption spectra, and atomic clocks (see, e.g. Flambaum & Berengut (2009)).

scholarly journals The LHC Higgs boson discovery: Implications for Finite Unified Theories

2014 ◽  
Vol 29 (18) ◽  
pp. 1430032 ◽  
Author(s):  
S. Heinemeyer ◽  
M. Mondragón ◽  
G. Zoupanos
Keyword(s):  
Higgs Boson ◽  
Predictive Power ◽  
Low Energy ◽  
Boson Mass ◽  
Higgs Boson Mass ◽  
Light Higgs Boson ◽  
Quark Masses ◽  
Grand Unified Theories ◽  
Unified Theories ◽  
Discovery Potential

Finite Unified Theories (FUTs) are N = 1 supersymmetric Grand Unified Theories (GUTs) which can be made finite to all-loop orders, based on the principle of reduction of couplings, and therefore are provided with a large predictive power. We confront the predictions of an SU(5) FUT with the top and bottom quark masses and other low-energy experimental constraints, resulting in a relatively heavy SUSY spectrum, naturally consistent with the nonobservation of those particles at the LHC. The light Higgs boson mass is automatically predicted in the range compatible with the Higgs discovery at the LHC. Requiring a light Higgs boson mass in the precise range of Mh= 125.6 ±2.1 GeV favors the lower part of the allowed spectrum, resulting in clear predictions for the discovery potential at current and future pp, as well as future e+e-colliders.

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